Attitude independent GPS ambiguity resolution using UKF

The vehicle's attitude should be known in advance in order to resolve GPS double differenced integer ambiguity when using motion-typed algorithm. To eliminate the dependence on the attitude, a novel algorithm for integer ambiguity resolution was investigated. Converting original vector measurement equation into scalar measurement equation, the attitude matrix of carrier vehicle was canceled out. After a short data collection period, a batch algorithm was employed to attain a coarse float estimate of the ambiguity. The batch algorithm included the centerted estimate algorithm and the whitening filter. Then the float ambiguity resolution was passed into an unscented Kalman filter as initial state value. UKF estimated the precise ambiguity resolution in real time with the initial value. Finally, simulation was implementeda and the results indicate that with the off-line batch algorithm UKF provides a correct ambiguity resolution without prior knowledge of vehicle's attitude, which validates the proposed algorithm.